One of the principal present day uses of hydrogen iodide is as a reagent in operating a chemical laser. These lasers include the important class of infrared (IR) lasers, based on the lasing action of vibrationally excited hydrogen fluoride (HF); hydrogen chloride (HCl); or hydrogen bromide (HBr). Such lasers operate, respectively, at wavelengths around 2700 nm, 3800 nm, and 4100 nm. Possible pumping reactions for these lasers are: EQU F+HI.fwdarw.HF+I (1) EQU Cl+HI.fwdarw.HCl+I (2) EQU Br+HI.fwdarw.HBr+I (3)
For more details relating to such lasers and reactions, the reader is referred to
(1) S. J. Arnold and K. D. Foster, D. R. Snelling and R. D. Suart, "A Purely Chemical HCl Laser", Appl. Phys. Lett. vol. 30 pp. 637-639, 1977. PA1 (2) S. J. Arnold, K. D. Foster, "A Purely Chemical HBr Laser" Appl. Phys. Lett. vol. 33 pp. 716-717, 1978. PA1 C. J. Hoffman, "Anhydrous Hydrogen Iodide", Inorganic Syntheses vol. 7 pp. 180-181, 1963. This process has the advantage of requiring only moderate temperatures (200.degree.-210.degree. C. at 760 torr pressure) and of using common industrial chemicals which are relatively easy to handle and store as starting materials.
There have been problems in the development of (chemical) lasers that use HI as a reagent. These have arisen from factors such as the high cost of commercially available HI, the limited shelf life thereof, and safety hazards associated with the storage of an appreciable quantity of a corrosive gas such as HI. Thus, there has remained a need for an inexpensive, reliable "on demand" technique or method of producing quantities of HI that is adequately pure and available in sufficient flow rates.
The liquid phase reaction of iodine with tetrahydronaphthalene (THN) EQU 2 I.sub.2 +C.sub.10 H.sub.12 .fwdarw.4HI+C.sub.10 H.sub.8 ( 4)
which converts iodine almost quantitatively to HI was the process chosen for the production of anhydrous HI. See the following text:
The process as described in the literature employs the dropwise addition of a very dilute solution of iodine in THN to a large volume of boiling THN. The present generator described herein overcomes the problem of the low solubility of iodine in THN and the necessity of boiling a large volume of liquid.